Buggy code:
public class WorkbenchPlugin extends AbstractUIPlugin { private static WorkbenchPlugin inst ; private EditorRegistry editorRegistry ; private DecoratorManager decoratorManager ; private ThemeRegistry themeRegistry ; private WorkingSetManager workingSetManager ; private WorkingSetRegistry workingSetRegistry ; public static boolean DEBUG = false ; public static String PI_WORKBENCH = PlatformUI . PLUGIN_ID ; private static char PREFERENCE_PAGE_CATEGORY_SEPARATOR = '//' ; private PreferenceManager preferenceManager ; private ViewRegistry viewRegistry ; private PerspectiveRegistry perspRegistry ; private ActionSetRegistry actionSetRegistry ; private SharedImages sharedImages ; private AboutInfo aboutInfo = null ; private IntroRegistry introRegistry ; public WorkbenchPlugin ( IPluginDescriptor descriptor ) { } public static Object createExtension ( final IConfigurationElement element , final String classAttribute ) throws CoreException { } protected ImageRegistry createImageRegistry ( ) { } public ActionSetRegistry getActionSetRegistry ( ) { } public static WorkbenchPlugin getDefault ( ) { } public IEditorRegistry getEditorRegistry ( ) { } public IElementFactory getElementFactory ( String targetID ) { } public IPerspectiveRegistry getPerspectiveRegistry ( ) { } public IWorkingSetManager getWorkingSetManager ( ) { } public WorkingSetRegistry getWorkingSetRegistry ( ) { } public IIntroRegistry getIntroRegistry ( ) { } public PreferenceManager getPreferenceManager ( ) { } public ISharedImages getSharedImages ( ) { } public IThemeRegistry getThemeRegistry ( ) { } public IViewRegistry getViewRegistry ( ) { } public IWorkbench getWorkbench ( ) { } protected void initializeDefaultPreferences ( IPreferenceStore store ) { JFacePreferences . setPreferenceStore ( store ) ; store . setDefault ( SHOULD_SAVE_WORKBENCH_STATE , false ) ; store . setDefault ( SHOULD_CLOSE_EDITORS_ON_EXIT , false ) ; store . setDefault ( SHOULD_SHOW_TITLE_BAR , true ) ; store . setDefault ( SHOULD_SHOW_MENU_BAR , true ) ; store . setDefault ( SHOULD_SHOW_TOOL_BAR , true ) ; store . setDefault ( SHOULD_SHOW_SHORTCUT_BAR , false ) ; store . setDefault ( SHOULD_SHOW_STATUS_LINE , true ) ; store . setDefault ( SHOULD_SHOW_PROGRESS_INDICATOR , false ) ; store . setDefault ( EDITORLIST_PULLDOWN_ACTIVE , false ) ; store . setDefault ( EDITORLIST_DISPLAY_FULL_NAME , false ) ; store . setDefault ( STICKY_CYCLE , false ) ; store . setDefault ( REUSE_EDITORS_BOOLEAN , false ) ; store . setDefault ( REUSE_DIRTY_EDITORS , true ) ; store . setDefault ( REUSE_EDITORS , 8 ) ; store . setDefault ( OPEN_ON_SINGLE_CLICK , false ) ; store . setDefault ( SELECT_ON_HOVER , false ) ; store . setDefault ( OPEN_AFTER_DELAY , false ) ; store . setDefault ( RECENT_FILES , 4 ) ; <START_BUG> store . setDefault ( VIEW_TAB_POSITION , BOTTOM ) ; <END_BUG> store . setDefault ( EDITOR_TAB_POSITION , TOP ) ; store . setDefault ( EDITOR_TAB_WIDTH , 3 ) ; store . setDefault ( OPEN_VIEW_MODE , OVM_EMBED ) ; store . setDefault ( OPEN_PERSP_MODE , OPM_ACTIVE_PAGE ) ; store . setDefault ( ENABLED_DECORATORS , "" ) ; store . setDefault ( EDITORLIST_SELECTION_SCOPE , EDITORLIST_SET_PAGE_SCOPE ) ; store . setDefault ( EDITORLIST_SORT_CRITERIA , EDITORLIST_NAME_SORT ) ; store . setDefault ( COLOR_ICONS , false ) ; store . setDefault ( SHOW_SHORTCUT_BAR , true ) ; store . setDefault ( SHOW_STATUS_LINE , true ) ; store . setDefault ( SHOW_TOOL_BAR , true ) ; store . setDefault ( MULTI_KEY_ASSIST , false ) ; store . setDefault ( MULTI_KEY_ASSIST_TIME , 1000 ) ; store . setDefault ( SHOW_FLOATING_PROGRESS , true ) ; PreferenceConverter . setDefault ( store , ERROR_COLOR , new RGB ( 255 , 0 , 0 ) ) ; PreferenceConverter . setDefault ( store , HYPERLINK_COLOR , new RGB ( 0 , 0 , 153 ) ) ; PreferenceConverter . setDefault ( store , ACTIVE_HYPERLINK_COLOR , new RGB ( 0 , 0 , 255 ) ) ; store . setDefault ( "ENABLE_CONFIGURABLE_PROJECT_WIZARD" , false ) ; store . setDefault ( "SINGLE_CLICK_METHOD" , DOUBLE_CLICK ) ; store . setDefault ( "ENABLE_COOL_BARS" , true ) ; store . setDefault ( "ENABLE_NEW_MENUS" , true ) ; store . setDefault ( "DISABLE_DIALOG_FONT" , false ) ; FontRegistry registry = JFaceResources . getFontRegistry ( ) ; initializeFont ( DIALOG_FONT , registry , store ) ; initializeFont ( BANNER_FONT , registry , store ) ; initializeFont ( HEADER_FONT , registry , store ) ; initializeFont ( TEXT_FONT , registry , store ) ; store . addPropertyChangeListener ( FontDefinition . getPreferenceListener ( ) ) ; store . addPropertyChangeListener ( new PlatformUIPreferenceListener ( ) ) ; } private void initializeFont ( String fontKey , FontRegistry registry , IPreferenceStore store ) { } public static void log ( String message ) { } public static void log ( String message , IStatus status ) { } public void setWorkbench ( IWorkbench aWorkbench ) { } public DecoratorManager getDecoratorManager ( ) { } public void startup ( ) throws CoreException { } private void initializeProductInfo ( ) { } public String getAppName ( ) { } public String getProductName ( ) { } public ImageDescriptor getWindowImage ( ) { } }

Fix:
store . setDefault ( VIEW_TAB_POSITION , TOP ) ;